The invention is based on a chain link, in particular of a curved conveyor chain, according to the preamble to claim 1.
A chain link of this kind, for example known from DE 32 35 224 A1, has a carrying device for holding material to be transported, such as work pieces or work piece supports. The carrying device has a head part in which at least one lateral bore is provided for pivotably supporting a pin of a first chain link adjacent to the head part. The head part is adjoined by a fork-shaped section, which is likewise disposed on the carrying device and has two legs that encompass the head part of a second chain link adjacent to the fork-shaped section. The legs are provided with lateral bores that are aligned with each other. The chain link has a pin, which is contained in the lateral bores of the legs and the head part of the second adjacent chain link. Projections protrude laterally from the legs in order to permit the chain link to be guided, particularly in the return side of a guide profile, and be driven by a driving wheel. The lateral bores of the legs also extend through the projections.
Since the pins extend over the entire external width of the projections, the conveyor chain is relatively heavy.
Since the projections are disposed around the pin, they have a reduced cross section due to the presence of the lateral bores. As a result, there is an increased stress concentration at this point. This reduces the drive forces that can be transmitted.
Since the pin is far away from a horizontal axis extending lateral to the longitudinal central axis through the center of gravity, when the conveyor chain is guided in the return side, a moment is produced, which causes the chain links to tilt around this center-of-gravity axis. As a result, an increased surface pressure is produced at the edges of the projections, which causes wear on these projections.
In driving wheels, which deflect the conveyor chain in one plane, the offset in relation to the above-mentioned horizontal axis likewise produces a moment, which can cause the conveyor chain to operate erratically. Particularly with small driving wheels that have only a few teeth, this also intensifies the so-called polygon effect. The polygon effect occurs in every conveyor chain. The greater the pitch and the smaller the number of teeth on the chain wheels, the more intense the polygon effect is.
In a conveyor chain composed of chain links according to DE 32 35 224 A1, the cylindrical design of the projections particularly has the advantage that in the driving wheels, which drive the conveyor chain in the plane, it is only possible for there to be point contact or linear contact with their gearing, thus setting the stage for a possible overloading of the plastic in the contact zone and for the occurrence of significantly greater wear.
WO 99/52798 has disclosed a chain link in which the projections on the legs are embodied underneath the lateral bores. When a driving wheel introduces a force, this also produces a moment, which can result in erratic operation.
The chain link according to the invention, in particular of a curved conveyor chain, with the characterizing features of claim 1, has the advantage over the prior art that no lateral tilting moment occurs since the projections are situated between the lateral bores of the legs and the at least one lateral bore of the head part. Since no bore therefore extends through the projections, there is also no cross sectional reduction and therefore no stress concentration, which makes it permits transmission of very powerful forces despite the low weight. Since the projections are situated as close as possible to the horizontal axis through the center of gravity, the moments occurring and consequently the wear, are reduced and the force and lever ratios are optimized.
In one advantageous modification, a receptacle for a threaded element such as a nut or hexagon bolt is provided on the underside of the carrying device, between the pin and the head part. This makes it easier to mount client-specific attachments onto the carrying devices.
Other advantages and advantageous modifications of the chain link according to the invention ensue from the dependent claims and the drawings.